The present invention relates to a method and apparatus for preparing chemical solutions, and more particularly, to a method and apparatus for preparing chemical solutions having high purity grades and used to fabricate electronic devices, such as semiconductor devices, from chemical gases having industrial chemical grades.
During the fabrication of electronic devices, such as semiconductor devices and LCDs, a wide variety of chemical solutions having different concentrations and different compositions are used in abundance as required in each fabrication process. Such chemical solutions are purchased from chemical makers.
Each type of chemical solution is stored in a reservoir tank, which is located in a fabrication plant, and replenished by tanker trucks in a liquid form. When replenishing the reservoir tank, an impurity may get mixed with and contaminate the chemical solution. Further, the storage of the chemical solution over a long period may change the concentration or composition of the chemical solution. A reduction in quality, or a lower purity, of such chemical solution may degrade the quality of the fabricated electronic devices.
Therefore, if the concentration of the chemical solution changes, the concentration is adjusted before usage, and if the chemical solution is contaminated by an impurity, the chemical solution is purified before usage. Such adjustment and purification takes time. Further, the purchase of chemical solutions increases the fabrication cost of the electronic devices.
Additionally, waste material, which includes chemical gases and liquids, must be reduced in semiconductor fabrication plants to protect the environment and comply with the ISO 14000 series of standards.